The present invention relates generally to band saws and more particularly to portable band saws for cutting boards from a log in situs.
Portable band saws have been provided mounted on a carriage that rides along a track to cut a board from a log that is supported above the track. Such equipment provides a platform for the track that is at least as long as the log to be cut, a carriage on extended legs that rides above and clears the log to be cut which is carried on a platform above the track and the bandsaw and its power drive are carried on the carriage. An example of such apparatus is described in U.S. Pat. No. 4,275,632 entitled "Portable Sawmill", which issued June 30, 1981 W. K. Ross. Similar apparatus is described in U.S. Pat. No. 4,519,283 entitled "Band Saw Mill", which issued May 28, 1985 to D. Sandborne and another similar apparatus is described U.S. Pat. No. 4,559,858 entitled "Portable Band Saw Saw Mill Apparatus", which issued Dec. 24, 1985 to Laskowski et al. These apparatus all include band saws, a carriage for the band saw, a track supported from the ground either directly on the ground or on a trailer and a support for the log that is also on the trailer and the carriage has extended legs so that the band saw carries rides above the log to be cut.
While these apparatus can be used to cut logs in situs, none of them can be used to cut a log lying on the ground, and while they are referred to as being portable, they are not hand portable and in fact are carried on a trailer and all require that the user somehow lift the log onto the apparatus for cutting. It is an object of the present invention to provide a hand portable band saw apparatus for cutting boards of variable thickness from a log lying on the ground.
A portable band saw according to the present invention uses the flat surface of a longitudinal cut from end to end of the log to ride on while making a subsequent cut. In order to make the first cut of a raw log and provide that flat surface, a surface must be provided for the portable band saw to ride on. It is another object of the present invention to provide apparatus that is readily installed on a raw log to provide a flat longitudinal surface for a band saw according to the present invention to ride on in making a first longitudinal cut of the log.
For any band saw, a guide at each of the band saw wheels is provided that bears against the straight edge (non-cutting edge) of the band and keeps the band from sliding off the wheel on the side thereof of the straight edge. Such a guide is usually a small roller on a bearing and axle carried on the band saw frame. However, no such guide is provided against the tooth edge (cutting edge) of the band, because the cutting edge would be damaged by a guide bearing against it and so would the guide. As a result, usually there is no guide to prevent the band from sliding off a wheel in the direction of the cutting edge of the band and so when the band does slide off the wheel in that direction the band is usually ruined and some of the band saw frame may also be damaged. It is another object of features of the present invention to provide means for preventing the band from sliding off a wheel in the direction of the cutting edge that does not damage the band teeth and/or holds the slipping band on the wheel long enough to enable the operator to stop the band saw drive.
Maintaining or adjusting a band saw band tension is usually done by shifting the position of the axle of the idler wheel. It is another object of features of the present invention to provide a mechanism shifting the position of the axle of the idler wheel under a resilient force that is adjustable so that the position of the axle is not fixed, but rather is subject to the resilient force acting against the band tension. It is a further object to provide such resilient force with a mechanical advantage against the band tension.
Moving the idler wheel relative to the driven wheel adjusts band tension. When the wheels and band are perfectly constructed and aligned in a common plane and the wheel axes parallel and there is no force on the band tending to move it off the wheel rims the band will stay centered on the wheel rims. However, such optimum conditions are seldom achieved and so not only must guards be provided to keep the band centered on the wheel rims, but also means may be provided for adjusting the alignment of the wheels. For example, means may be provided for tilting the plane of one of the wheels with respect to the other to make such adjustments. It is another object to provide means for tilting the plane of the idler wheel with respect to the plane of the driven wheel.